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The DNA of David Bain's brother Stephen was on bloodstained clothing the accused murderer wore on the morning his family were killed, his trial was told yesterday.

Environmental Science and Research forensic scientist Sally-Ann Harbison told the High Court in Christchurch she found the DNA of Stephen Bain on the T-shirt, shorts and a sock David Bain was wearing when police arrived at his Dunedin home on June 20, 1994.

Bain, 37, is being retried on charges of shooting dead his parents and three siblings.

The prosecution says Stephen, 14, fought for his life in a bloody struggle between him and his killer.

Bain claims the killer was his father, Robin Bain, 58, and that he turned the rifle on himself after shooting the family.

Dr Harbison told the court she also found Stephen's DNA on the rifle used in the killings, and on curtains in the lounge where the rifle and Robin's body were found.

In 1997 and 2003, Dr Harbison used samples taken from apparent bloodied areas on various items to try to match to the DNA of members of the Bain family. Such testing was not available at the time of Bain's first murder trial in 1995.

When Dr Harbison examined samples from bloodstains on David's sock, she found three samples matched Stephen's DNA.

Stephen's DNA was also in samples from blood on the front left, upper back and lower back of David's white T-shirt, and in a sample taken from a bloodstain on David's black shorts.

A spot of blood on the edge of a curtain, where the Bains' lounge led to a computer alcove, also contained Stephen's DNA.

The prosecution says Bain shot Robin through these curtains.

Stephen's DNA was also found where adhesive tape had been put on the rifle, where a strap attached to the rifle, and on the end of the rifle's telescopic sight, Dr Harbison said. Samples taken from Robin Bain's bloodstained clothing were also tested, and the only full results were his own DNA.

Questioned by defence lawyer Paul Morten, Dr Harbison said it was possible human DNA could be picked up through substances other than blood and through "well-handled items".

THE CASE SO FAR* After 36 days of the High Court murder trial of David Bain, the prosecution has called more than 100 witnesses. * About 10 Crown witnesses remain, and the prosecution case is expected to conclude next week. * The defence will then open its case. It is expected to call between 40 and 60 witnesses, possibly including David Bain.